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CPX4 drone in flight. France's Millau Viaduct bridge is seen in the background. Drones are aerial vehicles that are used for a wide range of surveillance purposes. Small drones like this are known as miniature UAVs (unmanned aerial vehicles). The CPX4 is a quadrocopter that uses four separate rotors to hover and move through the air for up to 30 minutes, powered by an electric motor. It has an ultrasonic obstacle avoidance system. CPX4 was developed from 2003 at the INP Grenoble University, France, and is now being developed by the Novadem company.